Direct Connecting Gun Assemblies for Drilling Well Perforations

ABSTRACT

A perforation gun assembly comprising a plurality of guns with a box fitting at one end and a modified pin fitting at the distal end; the modified pin fitting further comprising an end cap secured to an internal charger carrier, aligning a plurality of shape charges with scallops in the gun casing; and having a pressure switch, which connects to an electrical connection point at the box end of a charger carrier in an adjacent gun. The end cap being captured between the pin of one gun and the internal edge of the mating gun to protect and channel blast force to the pressure switch.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and expands on the inventor's previously filed applications: U.S. Ser. No. 15/312,120, “Apparatus for Electromechanically Connecting a Plurality of Guns for Well Perforation” filed 17 Nov. 2016; U.S. Ser. No. 15/586,439, “Apparatus and Method for Quick Connect of a Plurality of Guns for Well Perforation”, filed 4 May 2017; and U.S. Ser. No. 15/615,553, “Electromechanical Assembly for Routing Electrical Signals in Guns for Well Perforation”, filed 6 Jun. 2017; each of which, by this statement, is incorporated herein by reference for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX

Not Applicable.

BACKGROUND OF THE INVENTION Field of the Invention

This invention refers in general to an integral assembly (a “perf assembly”) of a plurality of perforating guns (“guns”) containing a plurality of shape charges (“charges”). This perf-assembly is used in perforation of wells during a drilling process. This invention is particularly directed to a new electro-mechanical assembly for joining a series of guns to allow reliable assembly and reliable sequential firing of the guns during the fracturing process of production wells. This process of well fracturing consists of safely assembling, wiring, lowering, detonating, and retrieving the residual materials of a plurality of shape charges in an assembly of perforating guns. The process perforates the well casing, the cement surrounding the casing in the bore hole, and causes cracking of the surrounding ground materials and rock formations. While this invention is generally found in the petroleum production industry, it may be equally applied to other environments of drilling production where perforation of well casing into the surrounding environment is necessary, such as water wells.

Background of the Invention

The perforation of petroleum wells is accomplished by lowering into the well a perf assembly comprised of a plurality of perforating guns each containing a plurality of shape charges oriented around the central axis. The guns are connected end to end and wired in sequence to a firing circuit which is in communication with a firing control at the surface. The plurality of guns is coupled by intermediate subs containing pass through openings for the wiring of firing signals and spacing to isolate explosive force of one gun from damaging those of an adjacent gun to be fired later in the sequence.

In previous applications intermediate subs were substantial in size and weight. They contained pass-through openings from end to end and side access compartments allowing access to interior wiring. These subs were often destroyed or damaged beyond repair during firing sequences. Other embodiments attempted to reduce this waste by developing smaller, less substantial subs where wiring was connected prior to joining the subs. These smaller subs were still damaged often, but the wasted materials and financial loss was reduced.

The method of joining a plurality of guns with intermediate subs with multiple connections means wires are often twisted, broken, or can pull loose during the assembly process by the act of screwing on subs and joining the components together. In short, more connections equal more potential problems. This results in assemblies having to be deconstructed and repaired. Additionally, weakened wires may pass initial test during construction only to fail during the process of lowering the assembly to depth, or due to vibrations of early charges in the sequence.

The preferred method is to fire the farthest/lowest gun first. Then, sequentially fire each gun back toward the well opening. This is because the explosion/pressure/debris from one gun's firing can possibly damage neighboring guns. Wires break, or connectors loosen during shockwave vibrations, or by blast force. Unfired guns are highly undesirable, as they are hazardous to bring to the surface due to the dangers of handling explosives which are not known to be in a safe condition or state.

To fulfill the operation briefly described above, while simultaneously respecting existing norms for the manipulation of explosives, highly capable operators must arm and assemble the guns at the wellhead, stripping the ends of insulated connecting wires and joining them in prescribed configurations, then re-insulating and protecting from sharp edges, crimping, etc. the exposed wires resulting in an ‘artisanal’ activity requiring skill and extreme caution.

It should be noted that petroleum production and exploration activities are generally located in areas with hostile climatic conditions for the operators; work hours are assigned in accordance to the needs of the operation and may include nighttime and daytime hours, with extreme cold or heat and rain or wind. Hours are controlled by working against the clock and by penalizing deadlines and other pressures. To that respect, it is necessary that the strictest safety norms be followed while handling explosive material; all of these factors taken together contribute to an increased likelihood that operators may commit errors while wiring or assembling the guns into a perf assembly to be introduced into the well. Further, even if the operators do everything correctly, the actions required to connect the pipe sections that make up the perf assembly may still produce a costly mistake.

From the above facts, there exists an obvious need to simplify the operation of arming and joining the guns into a perf assembly. There is also a need to ensure that the firing of one gun does not introduce faults into the remaining portions of the perf assembly preventing the required firing sequence. The object of this invention deals with the means to perform the electromechanical connection of the gun assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of an assembly of multiple armed and assembled guns in a manner that is utilized in the industry.

FIG. 2 shows a cross section of a single gun joined on each end to an adjacent gun.

FIG. 3 shows a cross section of an intermediate sub containing a pressure switch joining two adjacent guns with pass through wiring.

FIG. 4 shows a cross section of a junction of two perf guns by an insulating contact pin contained within an intermediate sub.

FIG. 5 shows a cross section of a reduced intermediate sub joining two adjacent guns.

FIG. 6A shows a perspective view of a pin end cap, in accordance with an exemplary embodiment of the invention.

FIG. 6B shows a cross section of the pin end cap from FIG. 6A.

FIG. 6C shows an end view of the pin end cap from FIG. 6A as viewed from the pin end of the gun.

FIG. 7A shows a perspective view of a box end cap as viewed from the box end of the gun, in accordance with an exemplary embodiment of the invention.

FIG. 7B shows a perspective view of the box end cap from FIG. 7A as viewed from the reverse angle.

FIG. 7C shows a cross section of the box end cap from FIG. 7A.

FIG. 8A shows a perspective view of a pressure switch retainer seal, in accordance with an exemplary embodiment of the invention.

FIG. 8B shows a cross section of the pressure switch retainer seal from FIG. 8A.

FIG. 9A shows a perspective view of an electrical insert to the box end cap from FIG. 7A, in accordance with an exemplary embodiment of the invention.

FIG. 9B shows a cross section of the electrical insert from FIG. 9A and its orientation/assembly with the box end cap from FIG. 7A.

FIG. 10 shows a cross section of a single gun with the pin end caps and box end caps, in accordance with an exemplary embodiment of the invention.

FIG. 11 shows a cross section close-up of adjacent guns with pin and box connection, joined and configured for discharge through direct connection of one gun to the adjacent gun in accordance with an exemplary embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In previous applications, which are referenced and incorporated above, the inventor discussed, inter alia, utilization of improved performance via specialized end caps on the charge carriers to protect the wires of other guns in the perf assembly during handling and blasting operations. However, connection of these assemblies required stringent spacing requirements, intermediate subs, and additional wiring components and connections to ensure assembling did not cause pressure switches and contact pins to prematurely activate, or fail to pass a firing signal rendering one or more guns inoperable.

By reconfiguring the charge carrier end caps to directly connect to neighboring guns without the need for intermediate wiring, and utilizing standard drilling pipe configurations of a pin on one end and a box on the distal end, reliable assembly with fewer connections and minimal waste components can be achieved to reduce resources and improve functionality of perforation operations in the industry.

In standard configurations, the end of the pipe box contacts the external shoulder of the pipe pin, and the pipe pin bottoms out against the internal shoulder of the pipe box in what is referred to as a double shoulder design. The double shoulder design provides a mechanical stop to the connection, a sealing surface, and friction to allow for greater torque. In the innovation described herein, the standard box configuration may be utilized unmodified at one end of the gun body casing. However, the pin end of the gun body casing must be modified in several critical ways.

The pin is shortened so the pin end cap of the charge carrier protrudes from the pipe on the pin end. The pin end cap is a cylindrical mass attached on an inner side to the charge carrier, and having an opening on the outer side for inserting and securing a pressure switch. The opening extends through the pin end cap to allow the wires of the pressure switch to extend into the charge carrier where they are connected to a detonator for the gun.

The pin end cap's inner end has a diameter less than the charger carrier tube, and is inserted into one end of the charge carrier and secured by screws through holes in the charge carrier threaded into the body of the pin end cap. External to the charge carrier, the pin end cap's diameter enlarges to approximately the inner diameter of the gun body casing, and includes a screw hole in one side threading into the side of the cylinder. A screw passes through a hole in the side wall of the gun body casing, and is recessed so as not to block the threads. This screw aligns the charger carrier to ensure the shaped charges therein are proximal to their corresponding scallops on the external surface of the gun body casing.

The pin end cap's external side further enlarges in diameter to create a step ring which has an outer diameter greater than the inner diameter of the gun casing, and less than the inner diameter of the pipe box. This step ring is secured between the shoulder at the bottom of the box, and the end of the pin, to protect one gun from the blast force of the adjoining gun.

External to the step ring, the outer end of the pin end cap's outer diameter reduces to less than the inner diameter of the gun body casing and contains a plurality of grooves for retaining O-rings. The O-rings seal the pin end cap against the inner wall of the adjoining gun body casing once assembled.

At the distal end of the charge carrier, i.e. the box end of the gun, the charge carrier is connected to a box end cap. The box end cap is a circular disk with a cylinder extending from one flat side toward the charge carrier. The cylinder walls are secured to the walls of the end of the charge carrier. The outer edge of the box end cap also extends toward the charge carrier to form a second larger diameter cylinder, which slides along the interior side wall of the gun body casing as the charge carrier is inserted or removed from the gun body casing, and ensures the charge carrier and gun body casing are coaxial.

The external side of the box end cap extends outward in a cylinder which supports one or more spring tabs which extend back into the charge carrier and connect with the firing signal wire running to the pressure switch on the distal end of the gun. In the preferred embodiment, the clips are secured to a conductive base which is secured to the end cap and electrically connected to the firing signal wire.

The clips are positioned to contact the electrical connector of the pressure switch secured in the pin end cap of the adjoining gun, but to allow the blast pressure to disengage the electrical connector and trigger the pressure switch, thus activating the wiring of the detonator of the adjoining gun for later firing sequences. One skilled in the art would appreciate other methods of securing fire signal wire to the electrical connector of the adjoining gun.

The pressure switch is secured in the pin end cap by a pressure switch retaining seal which is secured to the inside of the pressure switch opening of the pin end cap, and flares outward from the electrical connector of the pressure switch to enclose the cylinder which supports the clips on the box end cap. The pressure switch retaining seal is compressible, so it will seal between the adjoining guns upon assembly to guide the blast force from one gun to the pressure switch of the next gun.

The plurality of guns may be assembled and tested in a more desirable environment, and secured by thread protectors for shipment to the drilling site. On site, the alignment screw is removed from the pin end and the charge carrier is partially withdrawn from the gun body casing to allow the detonator to be wired to the pressure switch. The charge carrier is then reinserted and aligned by the alignment screw.

Once aligned, screwing the pipe threading of the pin and box ends of the guns together forces the electrical contact of the pressure switch in one gun to connect to the clips in the box end connector of the adjacent gun, and the pressure switch retaining seal deforms as the step ring of the pin end cap is secured between the shoulder at the bottom of the box, and the end of the pin, thus completing the connections.

Should disassembly be required, unscrewing the pipe thread would pull the electrical contact of the pressure switch from the clips of the adjoining gun. The pressure switch retaining seal may return to shape, or possibly require replacement depending on the elasticity of the construction material. At this point the thread protectors can be replaced and/or the detonator may need to be removed.

DETAILED DESCRIPTION OF THE DRAWINGS

The following is a detailed description of exemplary embodiments to illustrate the principles of the invention. The embodiments are provided to illustrate aspects of the innovation, but the invention is not limited to any embodiment. As those skilled in the art will appreciate, the scope of the invention encompasses numerous alternatives, modifications, and equivalent.

FIG. 1 is a cross-section of an assembly of multiple armed and assembled guns in a manner that is utilized in the industry. The perf assembly (1) has a firing head (2), a plurality of perforating guns (3), each containing a charge carrier, two tandem subs (4), and a bottom sub (5). In such a configuration, the tandem subs (4) may contain access ports (6) for accessing internal wiring during assembly.

FIG. 2 shows a cross section of a single gun joined on each end to an adjacent gun. In the example shown, a tandem sub assembly is associate with each gun, as is standard in the industry. The gun (3) comprises a charge carrier (13) with a plurality of explosive shape charges (16) joined by a detonation cord or fuse (19). The charge carrier (13) is supported, substantially centered, within the gun body casing (12) by an insulating top end (14) and an isolating bottom end (15). The top and bottom ends of the charge carrier may be one of several configurations, some of which are described in the applicant's other innovation descriptions incorporated above. The specifics of the top and bottom ends are not significant to the innovation described in this specific application.

One can see in the interior of the carrier (13) that the shaped charges (16) are shown set in radial fashion perpendicular to the gun wall, to the carrier, and, when the guns are within the well, to the well casing. In the illustration, six shape charges are illustrated, but the actual number and orientation will vary.

The shaped charges are explosives set in such a manner that they concentrate the force of the explosion outward, generating a jet of gas (plasma) at high pressure and temperature, that pulls the metal from the interior of the charge and projects it outward until it arrives at the well formation; with this action, the charges produce a perforating effect that is variable in proportion to the potency of the charges. It is well known practice to scallop the gun body casing to reduce the force necessary to pierce the casing at the desired location, and so that burrs formed from the perforation do not damage the walls of the well during later extraction of the gun after firing.

In each intermediate joint or intermediate sub or tandem sub (4) one can see the pressure activated changeover switch (17) referred to as the pressure switch, from which wires extend to the rest of the assembly. When the detonator is activated, a detonation is propagated by way of a “fuse”—or detonating cord (19)—to each of the shaped charges in the carrier (13) that burst in simultaneous fashion within the corresponding gun (3).

FIG. 3 shows a cross section of an intermediate sub containing a pressure switch joining two adjacent guns with pass through wiring. The gun body casing (12) of each gun has a box end with the charge carrier (13) terminated by a end cap (400) and secured in the gun body casing (12) by a snap ring (600). The intermediate sub (4) has two pin ends, a pass through opening for wiring, and the option of inserting a pressure switch (12) at either end to ensure it is close to the anticipated blast direction. In the left side gun, a spring-loaded connector pin (500) contacts the electrical contact of the pressure switch (17), which is held in the tandem sub (4) which was previously wired (F and G) to the adjoining gun.

FIG. 4 shows a cross section of a junction of two perf guns by an insulating contact pin contained within an intermediate sub. The insulating contact pin (610) is also known as a propagator. The purpose is to connect the fire signal wire between the two guns across the intermediate sub or tandem sub (4). The propagator (610) connects to the insulating contact pins (500) of either gun's charge carrier (13). The charger carrier (13) is centered in the gun body casing (12) by a connector end cap (400) and secured by a snap ring (600). The purpose is to electrically connect the fire signal wires (F, not shown) of the two guns, and without the potential to exert excess force on the pressure switch (17, not shown), possibly prematurely triggering it and thus disarming the lower guns.

FIG. 5 shows a cross section of a reduced intermediate sub joining two adjacent guns. The reduced intermediate sub (900) has pin pipe connections at both ends and is joining two adjacent gun casings (12) with box pipe connections at both adjoining ends. This configuration utilizes a specialized end cap (700) on the left charge carrier (13) which has an opening for a pressure switch (17). The pressure switch (17) is wired to the left gun then secured to the end cap (700) by threading (940) the intermediate sub (900). O-rings (950) help to seal the joint. The right gun case (12) has a charge carrier (13) ending in another specialized end cap (400) which accommodates a spring-loaded insulated pin (500) which mates with the pressure switch (17) when threaded to the opposite end of the intermediate sub (900).

FIG. 6A shows a perspective view of a pin end cap, in accordance with an exemplary embodiment of the invention. FIG. 6B shows a cross section of the pin end cap from FIG. 6A. FIG. 6C shows an end view of the pin end cap from FIG. 6A as viewed from the pin end of the gun.

The pin end cap (1100) has an inner face (1110) oriented toward the charge carrier (13, not illustrated), and a distal outer face (1120) oriented toward the adjoining gun. The outer end's diameter has a plurality of recesses (1130) for O-rings which seal against the interior surface of the corresponding gun body casing. A step ring (1140) is larger than the interior of the gun body casing, but small enough to slide into, and bottom against the interior shoulder of the threaded box end of the adjoining gun.

The pin end cap (1100) is secured to the interior surface of the pin end of the gun body casing with an alignment screw (1150) which also serves to align the shape charges of the charge carrier with the scallops on the exterior surface of the gun body casing. The charge carrier is secured to the pin end cap (1100) by screws through the carrier sidewalls oriented into the screw holes (1145) on the pin end cap. A pass through (1160) along the axis of the pin end cap (1100) allows the pressure switch (17, not shown) to be inserted through the outer face (1120) with the wires extending into the charge carrier to connect with the detonator (19, not shown). The outer face (1120) may be recessed and/or may have screw holes, or other connection points for support of legacy systems.

FIG. 7A shows a perspective view of a box end cap as viewed from the box end of the gun, in accordance with an exemplary embodiment of the invention. FIG. 7B shows a perspective view of the box end cap from FIG. 7A as viewed from the reverse angle. FIG. 7C shows a cross section of the box end cap from FIG. 7A.

The box end cap (1200) is a circular disk with an inner side (1210) and an outer face (1220). A charge carrier mating surface (1240) is a cylinder extending from the inner face (1210), and containing two screw holes (1245) for securing the charge carrier. The outer edge (1230) of the box end cap (1200) forms a second larger diameter cylinder, to center the charge carrier within the gun body casing.

The external side of the box end cap extends outward in a cylinder (1250) which supports one or more spring tabs of an electrical connector illustrated below which is secured to the box end cap through a screw hold (1260).

FIG. 8A shows a perspective view of a pressure switch retainer seal, in accordance with an exemplary embodiment of the invention. FIG. 8B shows a cross section of the pressure switch retainer seal from FIG. 8A.

The pressure switch retainer seal (1300) has a retainer end (1310) which surrounds the electrical contact of the pressure switch and hold it into the pin end cap's pass through (1160) by a plurality of friction rings (1320). The pressure guide end (1330) of the pressure switch retainer seal (1300) has a mating surface (1340) which contacts against the outer surface (1220) of the box end cap (1250) and encompasses the cylinder (1250) supporting the electrical clips (1450).

FIG. 9A shows a perspective view of an electrical insert to the box end cap from FIG. 7A, in accordance with an exemplary embodiment of the invention. FIG. 9B shows a cross section of the electrical insert from FIG. 9A and its orientation/assembly with the box end cap from FIG. 7A.

The electrical insert (1400) has a cylindrical mass (1410) which is electrically conductive and provides structural support. Two opposing spring clips (1450) have conductive ends (1459) which mate with the mass (1410) through two opposed holes (1420). The clips (1450) are oriented by retainer sections (1457) between the mass (1410) and the box end cap (1200) into the clip support ring (1250) where the ends are curved back upon themselves to provide a spring connection (1455). The electrical components are then secured to the box end cap by a screw (1440) passing through the end cap hole (1260) and the mass (1410) to the fire signal wire (F) and secured with a retaining nut (1445).

FIG. 10 shows a cross section of a single gun with the pin end caps and box end caps, in accordance with an exemplary embodiment of the invention. The charge carrier (13) with the shape charges (16) terminates at the box end (25) of the gun casing body (12, not labeled) with the box end cap (1200) and its electrical insert (1400) carrying the fire signal wire (F, not labeled).

At the distal end, the pin end (27) of the gun casing body (12, not labeled), the detonator (19) connects to the pressure switch (17) held into the pin end cap (1100) by the pressure switch retainer seal (1300). The alignment screw (1150) ensure the shape charges (16) are oriented correctly in respect to the scallops in the exterior surface of the gun body casing (12, not labeled).

FIG. 11 shows a cross section close-up of adjacent guns with pin and box connection, joined and configured for discharge through direct connection of one gun to the adjacent gun in accordance with an exemplary embodiment of the invention.

The diagrams in accordance with exemplary embodiments of the present invention are provided as examples and should not be construed to limit other embodiments within the scope of the invention. For instance, heights, widths, and thicknesses may not be to scale and should not be construed to limit the invention to the proportions illustrated. Additionally, some elements illustrated in the singularity may be implemented in a plurality. Some element illustrated in the plurality could vary in count. Some elements illustrated in one form could vary in detail and should be interpreted as illustrative for discussing exemplary embodiments. Such specific information is not provided to limit the invention.

The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications. 

1. A gun assembly for perforating wells comprising: at least one gun having a gun body casing, the casing being a hollow cylinder, with a box fitting at one end, and a modified pin fitting at the distal end; the modified pin fitting comprising a length of external thread shorter than the length of internal thread located in the box fitting; and an alignment point for accepting an alignment pin; a charge carrier, the charge carrier being a hollow cylinder, with exterior diameter less than the interior diameter of the casing; a pin end cap secured to the pin end of the charge carrier and extending the charge carrier to a length approximately equal to the length of the casing, physically securing and electrically grounding the charge carrier to the casing; the pin end cap further having an opening passing through the pin end cap for receiving a pressure switch secured therein; a plurality of shape charges inside the charge carrier, the charges disposed radially toward the external circumference and inter connected by a detonator cord; the detonator cord connecting with a detonation circuit within the charge carrier; a plurality of scalloped recesses in the casing adjacent to, and aligned with each of the plurality of charges; an alignment pin securing the charge carrier within the casing such that the charges are aligned with the scalloped recesses in the gun body.
 2. The gun assembly of claim 1 wherein the gun further comprises: a box end cap, secured to the box fitting end of the charge carrier, having an exterior diameter substantially equal to the interior diameter of the casing; the box end cap having an edge extending to one side of the external diameter of the box end cap, and biased outward from the central axis to substantially center the charge carrier within the casing.
 3. The gun assembly of claim 2 wherein the box end cap further comprises: an electrical connection point extending from the center of the box end cap's external side; the connection point being electrically isolated from the casing and from the charge carrier, and a wire connected from the electrical connection point, extending through the charge carrier, to the detonation circuit within the charge carrier.
 4. The gun assembly of claim 3 wherein the electrical connection point of the box end cap is electrically connected to a firing circuit for remotely detonating one or more guns individually.
 5. The gun assembly of claim 1 wherein the pin end cap further comprises: a first diameter less than the charge carrier end; a second diameter larger than the charge carrier end, and smaller than the internal diameter of the casing; a third diameter larger than the internal diameter of the casing, and smaller than the diameter of the internal thread of the box fitting, wherein the third diameter is captured between the end of the modified pin fitting of the casing, and the interior shoulder of the box fitting of a mated casing; a fourth diameter smaller than the smallest diameter of the mated casing's box fitting, the fourth diameter having at least two grooves for O-rings around the circumference, the O-rings mating against the interior cylinder of the smallest diameter of a mated casing's box fitting.
 6. The gun assembly of claim 1 wherein the pin end cap further comprises an alignment point for accepting an alignment pin mating with the alignment point of the gun casing.
 7. The gun assembly of claim 1 wherein the pressure switch is secured in the central opening of the pin end cap with a retainer seal such that the pressure switch's contact pin extends through the seal and is surrounded by a pressure guide directing blast pressure from a mated gun to the contact pin.
 8. The gun assembly of claim 1 wherein the gun assembly is comprised of connecting a first gun, of the at least one gun, to a second gun; by mating the modified pin fitting of the first gun to the box fitting of the second gun.
 9. The gun assembly of claim 8 wherein the mating of the guns electrically connects the pressure switch's contact pin of the first gun roan electrical connection point of the box end cap of the second gun. 